Conventionally, a transfer ribbon is placed over a card, and desired image data is transferred to the card by means of a thermal head.
This ribbon is coated uniformly with a sublimating dye which is transferred to the card by the action of heat. Substances which are capable of transferring dyes are limited to for example polyester, acrylic resin and polyvinyl chloride.
Japanese Patent Laid Open No. Sho 63-81093 proposes a two step transfer process wherein other substances can be used to transfer the image. According to this process, a rotating drum and a thermal head are provided as a mechanism for transferring transfer ink to an adhesive layer on a transfer film.
In the first step, the transfer film having the adhesive layer is placed on the rotating drum, the transfer ribbon having the sublimating dye is placed over the adhesive layer of the film, and an image is written on the adhesive layer by the thermal head.
In the second step, the image on the transfer film and the adhesive layer are heated and pressed onto a card by a heating roller so as to transfer the image to the card.
In the first step of the aforesaid process, an elastic layer consisting of chloroprene rubber may be provided on the drum surface to improve the contact between the transfer film and the ribbon. However, when heat is applied, the heat is transmitted to the elastic layer through the transfer ribbon and film, and sometimes causes the elastic layer to rupture.
In the first step, if an elastic layer consisting of silicone rubber is provided on the drum surface, the elastic film does not rupture. In this case however the transfer film does not slip easily, air enters between the silicone rubber and the transfer film, and if the surface is dirty, air gaps with the transfer film can easily form. If there are such air, gaps, image quality deteriorates, little heat is transmitted from the transfer film to the elastic layer, and heat from the thermal head accumulates in the film. This may cause heat rupture of the base tape of the ribbon, and tearing.
Further, the transfer ink has thermoplasticity. Consequently in the second step, if the film and the card are in contact with each other for a long period after the image is transferred to the card, the ink on the card may be re-transferred to the film when the temperature falls, leading to a deterioration of the quality of the image on the card. Further, as the transfer film is thin, the film tends to wrinkle when the image is applied by the roller to the card by heating under pressure so that the quality of the image transferred to the card again deteriorates. The film is continuously stretched from the image writing part to the transfer part so that if any wrinkles form in the transfer part, they will extend to the image writing part which is upline from the transfer part, and continuous image transfer will then no longer be possible.